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Scientists Open Electrical Link to Living Cells

The Terminator. The Borg. The Six Million Dollar Man. Science fiction is ripe with biological beings armed with artificial capabilities. In reality, however, the clunky connections between living and non-living worlds often lack a clear channel for communication. Now, scientists with the Lawrence Berkeley National Laboratory (Berkeley Lab) have designed an electrical link to living cells engineered to shuttle electrons across a cell's membrane to an external acceptor along a well-defined path. This direct channel could yield cells that can read and respond to electronic signals, electronics capable of self-replication and repair, or efficiently transfer sunlight into electricity.

"Melding the living and non-living worlds is a canonical image in science fiction," said Caroline Ajo-Franklin, a staff scientist in the Biological Nanostructures Facility at the Molecular Foundry. "However, in most attempts to interface living and non-living systems, you poke cells with a sharp hard object, and the cells respond in a predictable way -- they die. Yet, in Nature many organisms have evolved to interact with the rocks and minerals that are part of their environment. Here, we took inspiration from Nature's approach and actually grew the connections out of the cell."

Coaxing electrons across a cellular membrane is not trivial: attempts to pull an electron from a cell may disrupt its function, or kill the entire cell in the process. What's more, current techniques to transfer cellular electrons to an external source lack a molecular roadmap, which means even if electrons do turn up outside a cell, there is no way to direct their behavior, see where they stopped along the way, or send a signal back to the cell's interior.

"We were interested in finding a pathway that wouldn't kill the living systems we were studying," said Heather Jensen, a graduate student at University of California, Berkeley whose thesis work is part of this publication. "By using a living system in electronics, we can one day create biotechnologies that can repair and self-replicate."

In their approach, Jensen, Ajo-Franklin and colleagues first cloned a part of the extracellular electron transfer chain of Shewanella oneidensis MR-1, marine and soil bacteria capable of reducing heavy metals in oxygen-free environments. This chain or "genetic cassette," Ajo-Franklin notes, is essentially a stretch of DNA that contains the instructions for making the electron conduit. Additionally, because all life as we know it uses DNA, the genetic cassette can be plugged into any organism. The team showed this natural electron pathway could be popped into a (harmless) strain of E. coli -- a versatile model bacteria in biotechnology -- to precisely channel electrons inside a living cell to an inorganic mineral: iron oxide, also known as rust.
 
 

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